<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body></body>
  <script>
    console.log("aaa" + "bbb");
    var a = "你好  ",
      b = "world";
    console.log(a + b);
    console.log(123 + "123");
    console.log(true + "bbb");
    console.log(undefined + "bbb");
    //其他数据类型与字符串进行+运算，会自动转化为字符型，再拼接
    console.log(10 + 20);
    console.log(("aaa" + "bbb").length); //输出最终字符串的长度
  </script>
</html>
